This is a two part phase I/II OpenLabel Trial inHIV infected Infants. Part A will assess triple combination therapy (ZDV, 3TC and Nevirapine). Part B will assess quadruple combination antiretroviral therapy (ZDV, 3TC, Nevirapine and 1592U89. Primary objectives are to assess the antiretroviral activity and "durability" of triple and quadruple drug regimens. The purpose of the study is to assess the antiretroviral activity of the drug regimens in this population. Specifically, the study will assessthe proportion of infants whose viral load drops less than 1,000 copies per mil after 12 weeks of study therapy. In addition, safety and tolerance of the triple drug regimen and quadruple regimen will be documented. (ACTG 356)